Iron golems not spawning (village mechanic)

Iron golems have stopped spawning.

To recreate error, make a new flat world, place 10 beds in succession, flank with workstations, spawn 10  villagers. (For ease of management I chose to encase the villagers so they can only work and sleep). Place 10 more beds. Encircle the villager at a distance of at least 8 blocks from any possible village center. Observe that villagers all work.

Expected result: Golems will spawn when every villager sleeps and works.

Observed result: Observed for an hour, no golems have spawned yet.